GMC 2008 Yukon Denali Owner's Manual page 114

The taillamps will flash and a chime will sound when the
power liftgate is moving.
CAUTION:
{
You or others could be injured if caught in the
path of the power liftgate. Make sure there is
no one in the way of the liftgate as it is
opening and closing.
Notice: If you open the liftgate without checking for
overhead obstructions such as a garage door,
you could damage the liftgate or the liftgate glass.
Always check to make sure the area above and
behind the liftgate is clear before opening it.
2-16
The power liftgate can be power opened and closed in
the following ways:
•
Press and hold the power liftgate button on the
Remote Keyless Entry (RKE) transmitter until
the liftgate starts moving. Remote Keyless Entry
(RKE) System Operation on page 2-5 for more
information.
•
Pressing the liftgate button on the center console.
•
Pressing the touchpad switch on the outside liftgate
handle.
Pressing the buttons, or touchpad switch a second time
while the liftgate is moving reverses the direction.
l
: The liftgate can also be closed by pressing the
power liftgate button next to the liftgate latch.
Press the button a second time during liftgate operation
to reverse that operation.